A. Field of the Invention
The present invention relates to a polarizer and a polarizer system, and more particularly to a large scale polarizer and a polarizer system employing the large scale polarizer.
B. Description of the Related Art
Generally, a liquid crystal display device (LCD) comprises upper and lower substrates placed to face each other with a specific interval by a spacer, and a liquid crystal (LC) layer formed between the upper and lower substrates. The upper and lower substrates respectively have electrodes with specific patterns on their faced sides. And an alignment layer is formed over the electrodes to impart a pretilt angle on the LC.
For aligning the alignment layer, it has been proposed to use a rubbing method, a photo-alignment method or the like.
The rubbing method comprises depositing an alignment material, such as polyimide (PI), on a substrate and imparting the pretilt on the LC by rubbing the substrate with a rubbing cloth. Using this method, it is possible to make a large scale LCD and to align the alignment layer relatively quickly.
In the above described rubbing process, however, defects are generated by the microgrooves of the alignment layer which cause a light scattering and a random phase distortion. Moreover, dust particles and electrostatic discharge are produced in the alignment layer, so that a thin film transistor of the substrate is damaged and the yield is decreased.
On the other hand, the photo-alignment method imparts the pretilt on the LC by irradiating an ultraviolet light over a substrate having a photo-alignment layer. Compared with the rubbing method, there is no electrostatic discharge or dust particles, and thus the low yield problem is obviated. Morever, it could control simultaneously the pretilt throughout the alignment layer, and this uniformly arrange the LC molecules. Therefore, there are several advantages, including preventing the random phase distortion or the light scattering from defects generated by the microgooves.
At this time, to obtain a linearly or a partially polarized ultraviolet light, a polarizer polarizing an incident light from a light source is used. Particularly, the characteristics of the polarizer used in the photo-alignment process require that it be possible to apply to the large scale, to use in the ultraviolet light range, and to have an endurance, a heat resistance and a high light-transmittance.
In the conventional polarizer, however, because it is small, it is difficult to apply to the photo-alignment process of a large scale LCD. And in the case of the polarizer having an absorptive mode on which polymers are deposited, the endurance and heat resistance properties are poor, the wavelength of incident light is limited.